1. Field of the Invention
The present invention relates to an LCD (Liquid Crystal Display) position determination apparatus for an LCD projector, and in particular, to an improved LCD position determination apparatus for an LCD projector which is capable of shortening an assembling time of a projector by facilitating adjustment or alignment of red (R), green (G) and blue (B) cells at an identical position by measuring the positions of R, G and B LCDs during installation of the LCDs at or along three surfaces of a prism.
2. Description of the Conventional Art
As shown in FIG. 1, the conventional prism type LCD projector includes a light source 1 generating a beam of white light, an ultraviolet and heat blocking filter 2 for blocking ultraviolet frequencies and heat from the light source 1, a micro-lens array unit 3 for uniformly concentrating light, a first color splitting filter 4 for passing red light and reflecting green and blue light, a second color splitting filter 5 for passing through blue light and reflecting green light, a condensing lens 6 for condensing or focusing light from the first color splitting filter 4, an LCD panel 7 having a plurality of cells forming a picture, a color mixing prism 8 fort red, green and blue colors, and a projection lens 9 for projecting the mixed light on a screen (not shown).
In the drawings, reference numeral 3a denotes a field lens, 3b denotes a relay lens, and 5a through 5d denote reflection mirrors.
In the conventional prism type LCD projector shown in FIG. 1, white light from the light source 1 is split into different colors. The images incident on the red, green and blue LCD panels 7 are mixed by the color mixing prism 8 and are projected on the screen using the projection lens
Here, in the LCD projection apparatus, three LCD panels 7 are used for red (R), green (G) and blue (B) light, respectively, and when the three LCD panels are correctly installed, it is possible to project a fill color image accurately on the screen.
In conventional projectors, in order to overcome the above-described problems, the positions of the R, G and B LCD panels are adjusted using the images projected on a screen by the projection lens 9 provided as a unit. However, this method has the following problems.
In order to adjust the upper and lower portions the R, G and B image, the adjustment is performed after adjustment of other systems such as a lighting system, a circuit, etc. At this time, a position adjusting terminal attached to the LCD panel(s) is blocked by a circuit unit which is assembled to the upper portion of the projector, and it becomes impossible to adjust the upper, lower, left and right portions of the R, G and B image.
In addition, since thee is a predetermined distance between the position adjusting terminal and the screen, one user checks the adjusting position while viewing the screen and another user actually adjusts the LCD cells, so that at least two persons are required for adjusting the apparatus, thus requiring increased time and manpower.
Moreover, when the performances of the projection lens is poor, since the boundary between the neighboring cells is unclear, it is impossible to correctly adjust the positions of the cells.
In another method for overcoming the above-described problems, the positions of the cells are measured or adjusted one corner at a time using a microscope or an automatic collimator. In this method, since only R, G and B image of one side is viewed through the ocular lens or eyepiece, the upper and lower right corners and the lower left corner of the cells are misaligned when adjusting the upper left corner as shown in FIG. 2. When adjusting the upper right corner as shown in FIG. 3, the upper left, lower left and lower right corners are misaligned.